[IoVM] Map compare missing

[superbobry]

Io> Map with("k", "v") == Map with("k", "v") 
==> false
Io> Map clone == Map clone
==> false

[ales-tsurko]

This is normal behaviour. For example it's true in JavaScript also:

// Map with("k", "v") == Map with("k", "v")
var map1 = new Map();
var map2 = new Map();

map1.set("k", "v");
map2.set("k", "v");

console.log(map1 == map2) // false

// Map clone == Map clone
var map3 = new Map();
var map4 = new Map();

console.log(map3 == map4); // false

@stevedekorte I suggest to close this issue.

[stevedekorte]

Why should this be the normal behavior?

[ales-tsurko]

Hmm... At first I thought that because they are different objects, but I ended with lists, that are different objects too, but comparable... I don't know then. For me it's expected (intuitive) behavior anyway :)

[stevedekorte]

I'm not sure why I didn't implement equality properly in the Map primitive. It's potentially an expensive operation though. I'm guessing part of it is that equality of arbitrary objects can be tricky and lead to reference loops. I'll try to take a look when I get a chance.

[stevedekorte]

Fixed. Added IoMap_compare as the Map tag's compare function. Maps are now equal iff they have the same keys and corresponding values compare as equal.

Io> Map with("k", "v") == Map with("k", "v")
==> true
Io> Map clone == Map clone
==> true
Io> Map with("a", 1) == Map with("a", 2)
==> false
Io> Map with("k", "v") == Map with("k", "v", "x", 1)
==> false

Maps of unequal size compare by size. Otherwise, iteration order doesn't matter — for each key in self, we look it up in the other map and compare values.

Commits:

• wasm branch: 9b5b76e
• master branch: 877fb94

Closing.